The navel orangeworm, Amyelois transitella, is a serious field insect pest of almonds in California resulting in the loss of millions of dollars to growers.
The female will attempt to oviposit (lay eggs) on a hullsplit nut prior to harvest or on a mummy or sticktight which is a nut which stays on the tree after harvest and cannot be dislodged. These nuts harbor overwintering pests.
Various insecticides and insect sex pheromones have been used to kill and/or disrupt communication between male and female insects and/or by ovipositonal disruption to encourage the laying of eggs on places other than the almonds. In such cases the larvae will die after hatching.
The purpose of ovipositional disruption is to release into the air one or more components of the odor of a certain object in order to make it difficult for the insect to locate that object by flying toward its odor. By releasing the disrupting agent into the air, the female is apparently unable to "smell" the object on which to oviposit, and in addition, the female may be stimulated to fly toward the artificial source(s) and lay eggs in inappropriate locations.
In U.S. Pat. No. 4,605,560, there is suggested a method and composition for the ovipositional disruption of the navel orangeworm. The method includes permeating the air or spraying almond trees with a composition of matter incorporating as an active ingredient, crude almond oil. The composition can include a water emulsion of a wettable powder formulation containing appreciably equal amounts of crude almond oil and ground almond press cake.
Crude almond oil is expressed from rejected almonds. The oil is refined and sold as a premium cooking oil. The press cake is the solid material which remains after the oil is expressed from the almonds.
The composition is applied as a spray of 5 gallons per acre crude almond oil in the form of a water emulsion.
Alternatively, 2 pounds per acre of a wettable powder formulation of crude almond oil plus almond press cake and adjuvant materials are applied as a spray.
The above application gave good suppression of egg laying and good control of larval infestations. This compares with the use of conventional insecticides as Sevin.
The patented method is desirable for use both from the standpoint of effectiveness and reduced cost compared with conventional insecticides.
However, it has been found that the application of the crude almond oil, alone or combined with almond press cake, can be phytotoxic to almond trees at certain concentrations causing the leaves to turn yellow and eventually to drop off. Moreover, the crude almond oil and the press cake have been found to contain aflatoxins which are potent carcinogens.
Accordingly, the above drawbacks have led to a search for another method for the ovipositional disruption of the navel orangeworm which has the same effectiveness but which is not phytotoxic to the almond tree at effective concentrations or contain aflatoxins.